A website has published purported leaked U.S. documents that it claims show the Obama administration has misrepresented the number of civilians killed by drone attacks against terrorist targets in the Middle East and South Asia.

The website The Intercept on October 15 said it received the documents detailing the drone program under President Barack Obama from a whistle-blower.

The site was co-founded by journalist Glenn Greenwald, who published the documents leaked by former U.S. intelligence contractor Edward Snowden.

The source said the U.S. routinely identifies as militants victims whose identity is unknown in an effort to depict drone strikes as precise and surgical.

According to the documents, in one five-month period, nearly 90 percent of drone-strike casualties were not the intended targets.

They described one mission called Operation Haymaker that purportedly killed more than 200 people in northeastern Afghanistan between January 2014 and February 2015. Only 35 of the victims were intended targets.

The documents indicate that the signals intelligence that the United States relies on for drone strikes is "poor and limited" in many countries such as Somalia and Yemen.

Asked about the report, White House spokesman Josh Earnest said program officials "go to great lengths to limit civilian casualties."